textproduct: Rapid City

KEY MESSAGES

- Marginal to Slight (Level 1-2 out of 5) risk of severe thunderstorms late this afternoon/evening with the primary risk of damaging winds, but large hail may also occur.

- Hot weather (Sunday looks hottest) will continue through the weekend with daily chances for active thunderstorms as ridge- riders rotate through the northern Plains.

UPDATE

Issued at 320 AM MDT Wed Jul 29 2026

Forecast remains on track for hot and unsettled conditions over the next few days. Sfc thermal ridge will develop over the area today with temperatures climbing into the upper 90s to around 100 across much of the western SD plains into northeastern WY. Some areas may reach criteria level heat indices, especially in our eastern zones. However, smoke aloft may impact afternoon temperatures and given that the heat indices will be borderline already and the smoke aloft may keep things slightly cooler, have opted to not issue any heat headlines at this time.

Decent shortwave riding over the ridge will cross the Northern Plains later today. ML CAPE values of 2000-3000 J/kg and 30-40kt of effective shear will support an isolated severe threat with inverted V soundings pointing to damaging winds as the primary risk, though 1+" hail is also possible with any severe storms that develop. "Cool" front will pass through the area later tonight, dropping highs tomorrow about 10 degrees.

DISCUSSION

(This Evening Through Tuesday) Issued at 1224 PM MDT Tue Jul 28 2026

18z surface analysis had weak trough from ND into central WY. Water vapour loop had upper ridge over CO/NM and building heights over the northern Plains - a distinct wave hard to find. 0.5km visible satellite loop had cu/tcu over Campbell County, and then near the western foothills of the Black Hills per downstream convergence given east/southeast flow on the western SD plains. Upper ridge continues to dominate the weather this week.

This afternoon/evening, 0.5-1KJ/kg MLCAPE will develop over northeastern WY/southwestern SD with 25-35kts effective shear and limited MLCIN. Isolated/scattered tsra will develop with a few storms capable of gusty winds. CAMs not particularly excited about organized convective prospect, probably owing to the rising mid- level heights. Guidance temperatures look fine.

Wednesday looks a little more interesting. Distinct shortwave trough will rotate around ridge and reach eastern MT/WY during peak insolation, impinging on surface trough. 1-1.5KJ/kg MLCAPE will have 25-35kts 0-6km bulk shear available. Forecast soundings suggest damaging wind will be the main threat, especially over northwestern SD, but some large hail not out of the question. NBM PoPs robust, but seem warranted given available synoptic scale forcing. Temperatures will be near guidance.

Thursday through the weekend will be very warm/hot. Sunday looks hottest right now per robust thermal ridge and preponderance of ensemble guidance. Perhaps some record highs in jeopardy by Sunday. Any day could feature active thunderstorms. The "cooldown" for the beginning/middle of next week still looks like it is there, but the signal keeps getting muted by differing ensemble solutions. Confidence remains low in sustained heat relief.

AVIATION

(For the 12Z TAFS Through 12Z Thursday Morning) Issued At 622 AM MDT Wed Jul 29 2026

Scattered TSRA will develop over northeastern WY into western SD this afternoon and evening. Brief MVFR conditions and wind gusts to 40-45kts will be possible near any storm cells. Outside of storms, VFR conditions expected through the TAF period.

FIRE WEATHER

Issued At 1224 PM MDT Tue Jul 28 2026

Elevated fire weather conditions are expected much of this week due to hot temperatures as well as minimum relative humidity in the teens and 20s. The joint probability of MinRH <15% and winds >25mph is low at this point through Friday. However, an increasing signal exists for critical fire weather conditions for Saturday through Monday if stronger winds are present. The cores of thunderstorms that occur this week should contain wetting rain, but lightning strikes outside of the cores as well as strong, erratic winds may create opportunities for new fires.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.